I. Field
The present disclosure relates generally to communication, and more specifically to techniques for transmitting multiple data streams in a communication system.
II. Background
In a communication system, a transmitter may transmit multiple data streams via multiple transmission channels to a receiver. The transmitter typically encodes and modulates (or symbol maps) the data for each stream prior to transmission in order to combat deleterious channel conditions. The receiver performs the complementary demodulation and decoding to recover the data sent by the transmitter. The coding and modulation performed by the transmitter have a large impact on the performance of the data transmission.
Rate selection refers to the selection of an appropriate coding and modulation scheme for each data stream to achieve a specified level of performance, which may be quantified by a target packet error rate (PER). Rate selection is challenging because the transmission channels may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-noise-and-interference ratios (SNRs). The SNR of a transmission channel determines its transmission capability, which is typically quantified by a particular data rate that may be reliably sent on the transmission channel. If the SNR varies from transmission channel to transmission channel, then the supported data rate would also vary from channel to channel. Furthermore, if the channel conditions vary with time, then the data rates supported by the transmission channels would also vary with time.
There is therefore a need in the art for techniques to perform coding and modulation for multiple data streams in a manner to achieve good performance and to simplify rate selection.